carbonfiber box

[Endless Lasers]

Has anyone here has any experiance in using carbonfiber for making the box

[inertial]

Hi,
A friend of mine have used it. Awesome rigidity and good damping.
Very reccomended

Cheers,
Paolo

[gedlee]

I made several speakers this way - I didn't think that it was worth the extreme cost.

[David Gatti]

What about fibreglass as a cheaper alternative?

[MJL21193]

Why not MDF, cheaper still.

[Endless Lasers]

Every material has its pro's and cons. Carbonfiber claims some properties which i cant check, and i am unfamiliar with the relation with indeed glasfiber or MDF. If the expensive carbonfiber is after practical ivesigation only 5% better than the cheapest material, than there is no real reason to use it.

[simon dart]

When you say carbon fibre, there are hundreds of ways to use this material. It can be thought of as similar to GRP, except that you use carbon fibres in an epoxy resin instead of glass in polyester. The priciple is the same.

If you look at racecar construction it is almost always used as a skin on a foam or honeycomb for stifness with low mass. You could use it along these lines like the Celestion SL600 which used an aluminum version of this type of construction called aerolam. Being very low mass it had very little stored energy but was totally acoustically transparent at certain frequencies, the designers had to cope with a lot, it was a very complex build.

You can see a different approach on Wilson-Benesch speakers. I believe they form a panel with moulded in stiffeners like I-beams but they only use it for the side panels.

You could go another other way with it, which in my view stands the most chance of success. A vacuum formed, autoclave cured enclosure of low resin content solid woven pre preg is likely to be incedibly inert and stiff if you make it 25mm thick. But it is sure to cost a medium sized fortune!

Study how its used in other applications and you will stand some chance of answering this question. I fear its no coincidence that you almost never see it used in speaker cabinet construction!

[gedlee]

The point is to use the lowest cost material that "gets the job done". Thats obviously going to be MDF with a good construction and internal bracing. I used a molded process to get very large radius corners that were difficult to do in MDF. But by simply using a radius small enough to be routed, then MDF becomes viable and is far and away the lowest cost alternative.

So if we are talking about the extremes of performance where the corner radius differences of an inch or less make a difference, then there might be some argument for composites like carbon fiber or figerglass. But for almost all typical cases of loudspeaker systems the edge diffraction will not be the limiting factor in performance and MDF is going to be the better (read lowest cost) approach.

[zimjj]

I guess I will use this reply as an introduction. My name is John, from Tucson, and I'm a new DIYer who just built his first project, a two way monitor with a Hiquphon OW-1 tweeter and a Scanspeak 15W/8530K-00. Now I'm hooked!

The reason I'm replying to this thread is because the use of carbon fiber, or fiberglass, occurred to me. I was looking at a very sculptural design for an enclosure and was trying to figure out how to make it out of plywood and or MDF. Then I remembered from a brief fling with radio controled model airplanes, which used very stiff foam wing cores that can reach a 10' wing span and support a 50 lb plane with a 15+ hp motor. They cut these cores to any shape desired usng a hot wire.

So I figured you could cut your shape out of this foam and lay up the fiber and resin as thick as you want. That's as far as I got in my thought process.

John

[gedlee]

This would not be an efficient process for enclosures. One wants to do something more akin to the way that sailboats are made. The better ones do use cores of foam or balsa, as I do in my enclosures, but this requires a mold. The molds are were the costs start to stack up.